How do I determine if a DNS error is upstream or specific to my server?

Introduction

You receive an error like this one in your browser when you attempt to access a site:

Unable to determine IP address from host name

This error indicates that the domain associated with the site does not resolve.

For troubleshooting purposes, it may be helpful to determine whether the DNS issue is occurring locally on your cPanel server or upstream on one of the nameservers above your cPanel server.

Procedure

Query the cPanel server directly from your local system for the IP address of the affected domain; if it returns the expected value, this indicates that the server and its firewall are functioning correctly and that the issue is occurring upstream. In this example, 198.51.100.24 represents your cPanel server's IP address, as well as the IP address of the domain:

user@local-system ~ % dig +short domain.tld @198.51.100.24
198.51.100.24